Cancer is in the first place among death cause diseases in Japan, and fatalities therefrom are way ahead of those from other diseases such as cardiac diseases and brain diseases. Cancer occurs in all organs and progresses to invade and metastasize to various organs. Thus, to perform effective therapy for cancer, it is most important to treat the cancer at a treatable stage by early detection. Currently, the development of various diagnostic methods and early detection by diagnosis have become possible, which leads to early therapy to prolong life. However, despite the development of various diagnostic and therapeutic methods, invasion and metastasis from a primary lesion complicate therapy and follow a course leading to death.
Liver cancer is a malignant tumor present in the liver. Liver cancer can be divided into a primary liver cancer occurring primarily in the liver and a metastatic liver cancer resulting from the metastasis of a cancer species having occurred in an organ other than the liver into the liver. As major malignant tumors occurring in the liver (primary liver cancers), there are hepatocellular carcinoma derived from liver cells and intrahepatic cholangiocarcinoma (or cholangiocellular carcinoma) derived from biliary epithelial cells. There is also a cancer considered to be their mixed type. Hepatocellular carcinoma (HCC) is a malignant tumor derived from liver cells and accounts for 90% or more of primary liver cancers. Almost all the hepatocellular carcinoma occurs from viral hepatitis. Intrahepatic cholangiocarcinoma (ICC) is a cancer accounting for 3% of primary liver cancers and is considered to find difficulty in early detection, have a low survival rate after surgical resection, be poorly responsive to chemotherapy, and have poor prognosis.
For the early detection of liver cancer, the development of a detection device using a tumor marker has previously been under way. For hepatocellular carcinoma, to date many markers for cancer detection have been developed. For example, α1 fetoprotein (AFP) is clinically used as a tumor marker for hepatocellular carcinoma, and PIVKA-II (New Eng. J. Med. 310: 1427-1431, 1984) is also utilized as a tumor marker for hepatocellular carcinoma. Other known examples of the tumor marker for liver cancer include CEA, CA19-9, KMO-1, DuPAN-2, Span-1, CA50, SLX, basic fetoprotein (BFP), NCC-S, T-439, alkaline phosphatase isozyme, γ-GTP isozyme, IAP, TPA, β2-microglobulin, ferritin, POA, and trypsin inhibitor (Japanese Unexamined Patent Application Publication No. 2002-323499).
In recent years, many tumor markers for hepatocellular carcinoma are disclosed, which consist of genes and polypeptides expressed in hepatocellular carcinoma. For example, tumor markers for hepatocellular carcinoma are disclosed, which consist of genes and polypeptides including Gla incomplete blood coagulation factor VII (Japanese Unexamined Patent Application Publication No. 08-184594), aldolase β gene, carbamoyl phosphate synthase I gene, plasminogen gene, EST51549, albumin gene, cytochrome P-450 subfamily 2E1 gene, retinol binding protein gene or organic anion transporter C gene (Japanese Unexamined Patent Application Publication No. 2004-105013), human gene ZNFN3A1 having zinc finger and SET domains (Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2005-511023), glypican-3 (GPC3) (Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2005-526979) as a heparan sulfate proteoglycan, and development and differentiation enhancing factor 1 (DDEFL1) (Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2005-503176) located in the region of chromosomal band 1p36.13 and controlling the reformation of the actin cytoskeleton.
In addition, tumor markers for hepatocellular carcinoma are disclosed, which consist of genes and polypeptides including the presence of deletion in the chromosome region 8p12, 16p13.2-p13.3, 16q23.1-q24.3 or 19p13.2-p13.3 (Japanese Unexamined Patent Application Publication No. 2006-94726), Wnt-1 encoding a secretory cysteine-rich protein family (Japanese Unexamined Patent Application Publication No. 2007-139742), genes of carbamoyl phosphate synthase L chain MGC47816 and protein HES6 comprising helix loop-helix main and orange domains (Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2007-506425), a cell-related hepatocellular carcinoma (HCC) protein consisting of SEMA5A (semaphorin 5A), SLC2A2 (solute carrier family member), ABCC2 (ATP-binding cassette subfamily C member 2) or HAL (histidine ammonia lyase) (Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2007-534722), or human α2,6 sialyltransferase (Japanese Unexamined Patent Application Publication No. 2007-322373).
A hepatocellular carcinoma marker in which attention is focused on a constitutive glycan group of a glycoprotein in the serum has recently been disclosed as a marker highly specific for hepatocellular carcinoma (Japanese Unexamined Patent Application Publication No. 2007-278803). The hepatocellular carcinoma marker consists of a hepatocellular carcinoma marker consisting of a trisialyl glycan disappearing or decreasing with the development of hepatocellular carcinoma; the detection of hepatocellular carcinoma using the tumor marker has been shown to be performed by using a labeled glycan and calculating the amount of the hepatocellular carcinoma marker prepared from a sample through separation using an ion-exchange column and analysis by an elution pattern in high performance liquid chromatography employing an ODS silica column.
Several tumor markers for detecting cholangiocarcinomas including intrahepatic cholangiocarcinoma are also disclosed. For example, Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2003-527583 discloses the use of a trypsinogen activation peptide (TAP) as a marker for detecting bile duct-pancreas cancer species; Japanese Unexamined Patent Application Publication No. 2005-304497 discloses the use of at least one genomic gene selected from the group consisting of ZNF131, DOC2, DAB2, PC4, SKP2, CDH10, CDH12, TERT, CDK5, BA11, PSCA, MLZE, RECQL4, BCL1, FGF4, ITGB4, Survivin, SRC, PTPN1, PCTK1, and CTAG, as a gene marker for cholangiocarcinoma; WO2005/023301 discloses the use of an anti-glypican 3 antibody as a diagnostic agent for cholangiocarcinoma; and Japanese Unexamined Patent Application Publication No. 2008-72952 discloses the use of nucleotides constituting the base sequence of one gene except claudin 4 or at least 2 genes selected from the group consisting of (1) insulin-like growth factor-binding protein 5 (IGFBP5), (2) claudin 4 (CLDN4), (3) PDZ and LIM domain 7 (PDLIM7), and (4) Biglycan (BGN), as a marker for detecting cholangiocarcinoma. The relation between cholangiocarcinoma and claudin 4 per se is reported in “Modern Pathology 19: 460-469 (2006)”.
From a standpoint of a strategy or the like for overcoming bile duct tumors including intrahepatic cholangiocarcinoma, the differential diagnosis of hepatocellular carcinoma, intrahepatic cholangiocarcinoma, and mixed-type hepatocellular carcinoma in which both of the components can be identified, in primary liver cancer is important. Cytokeratin has previously been used as a tissue marker, and attention has recently been given to new markers such as EpCAM. However, because these existing markers show positivity in not only cholangiocarcinoma but also the normal bile duct and the peripheral interstitial area, there is a need for the development of a marker more specific for cholangiocarcinoma (Cytokeratinl: Oncology Rep. 17: 737-741, 2007; Cytokeratin2: Med.Pathology 9: 901-909, 1996; EpCAM1: Gastoroenterology 136: 1012-1024, 2009; EpCAM2: Cancer Res. 68: 1451-1461, 2008).
As described above, for the early detection of liver cancers such as hepatocellular carcinoma and intrahepatic cholangiocarcinoma, many markers for detecting cancer are disclosed; however, since most of the tumor markers are tumor markers for liver cancer consisting of genes or polypeptides expressed in liver cancer, they impose many constraints as detection device for early detecting and diagnosing liver cancer to be accurately and simply used on a clinical site in view of problems of clinical applicability such as a complex operation for detecting the gene expression and the detection precision for specifically detecting a cancer species and in terms of the sensitivity and precision of the differential diagnosis of a cancer species or the cancer detection, and are therefore not necessarily satisfactory. The method for detecting the occurrence of liver cancer using a gene expressed in liver cancer as a tumor marker cannot also be applied to a case where bile or the like is used as a test specimen.